Development of an Interception Glove Sampler for Skin Exposures to Aromatic Isocyanates

Development of a new SPE UPLC-MS/MS method for extraction and quantitation of toluene diamine on gloves following toluene diisocyanate exposure

RATIONALE

Toluene diisocyanate (TDI) is a highly reactive isocyanate commonly used as a mixture of 2,4- and 2,6- isomers in the production of flexible foams. Exposure to TDI occurs primarily through vapour inhalation in workplaces where TDI is produced or used, but dermal exposure is also possible during some tasks. To ensure workplace safety, accurate monitoring of TDI and toluene diamine (TDA) levels is required. Methods of quantifying field effectiveness of gloves in preventing dermal exposure have not been established. Therefore, there is a need to develop a new practical method for assessing glove effectiveness for TDI/TDA.

METHOD

A new offline SPE UPLC-MS/MS method for the quantitation of TDA isomers from TDI-exposed gloves was developed. Gloves were dipped in a solution of 1% acetic acid leading to a full conversion to TDA. TDA-free amine compounds were derivatized with acetic anhydride to increase chromatographic retention and signal intensity.

RESULTS

2,4-Diaminotoluene-α, α, α-d3 (2,4-d₃ -TDA) was selected as a surrogate standard to minimise the variability in sample preparation and instrumental sensitivity. The choice of UPLC-MS/MS operated in multiple reaction monitoring (MRM) mode allowed to reach much lower limits of detection (LOD). The LOD of the method was 6.86 and 2.83 ng/mL (0.03 and 0.01 μg) for 2,6-TDA and 2,4-TDA, respectively. The limit of quantitation (LOQ) was 22.85 and 9.42 ng/mL (0.11 and 0.05 μg) for 2,6-TDA and 2,4-TDA, respectively.

CONCLUSION

A new UPLC-MS/MS analytical method has been developed to determine field effectiveness of gloves for preventing dermal exposure to TDI/TDA. The new technique overcomes some limitations for measuring putative dermal exposure to isocyanates and may be useful in exposure monitoring and future research on isocyanate health risks.

Toluene diisocyanate occupational exposure data in the polyurethane industry (2005-2020): A descriptive summary from an industrial hygiene perspective

This article provides an overview of toluene diisocyanate (TDI) workplace air concentration data. Data were collected between 2005-2020 in workplaces across the United States, Canada, and the European Union by a number of different organizations, primarily using the sampling procedures published in OSHA Methods 42 and 5002. The data were then collated and organized by the International Isocyanate Institute. Air samples were collected from several market segments, with a large portion of the data (87%) from the flexible foam industry. The air samples (2534 in total) were categorized into "area" or "personal," and the personal samples were subcategorized into "task," "short term," and "long term." Most of the air sample concentrations (87%) were less than 5 ppb. However, the presence of airborne TDI greater than 5 ppb indicated the importance of respiratory protection in some situations; therefore, respirator use patterns were studied and summarized. Additionally, this article provides a summary of air sample concentrations at different flexible foam manufacturing job roles. The information on air sampling concentrations and respiratory protection during TDI applications collected in this paper could be useful for product stewardship and industrial hygiene purposes in the industries studied.

Assessment of personal inhalation and skin exposures to polymeric methylene diphenyl diisocyanate during polyurethane fabric coating

Methylene diphenyl diisocyanate (MDI) monomers and polymeric MDI (pMDI) are aromatic isocyanates widely used in the production of polyurethanes. These isocyanates can cause occupational asthma, hypersensitivity pneumonitis, as well as contact dermatitis. Skin exposure likely contributes toward initial sensitization but is challenging to monitor and quantitate. In this work, we characterized workers' personal inhalation and skin exposures to pMDI in a polyurethane fabric coating factory for subsequent health effect studies. Full-shift personal and area air samples were collected from eleven workers in representative job areas daily for 1-2 weeks. Skin exposure to hands was evaluated concomitantly with a newly developed reagent-impregnated cotton glove dosimeter. Samples were analyzed for pMDI by liquid chromatography-tandem mass spectrometry. In personal airborne samples, the concentration of 4,4^'-MDI isomer, expressed as total NCO, had a geometric mean (GM) and geometric standard deviation (GSD) of 5.1 and 3.3 ng NCO/m³, respectively (range: 0.5-1862 ng NCO/m³). Other MDI isomers were found at much lower concentrations. Analysis of 4,4^'-MDI in the glove dosimeters exhibited much greater exposures (GM: 10 ng/cm²) and substantial variability (GSD: 20 ng NCO/cm²; range: 0-295 ng NCO/cm²). MDI inhalation exposure was well below occupational limits for MDI for all the job areas. However, MDI skin exposure to hands was substantial. These findings demonstrated the potential for substantial isocyanate skin exposure in work settings with very low airborne levels. This exposure characterization should inform future studies that aim to assess the health effects of work exposures to MDI and the effectiveness of protective measures.

Characterization and Quantitation of Personal Exposures to Epoxy Paints in Construction Using a Combination of Novel Personal Samplers and Analytical Techniques: CIP-10MI, Liquid Chromatography-Tandem Mass Spectrometry and Ion Chromatography

Epoxy resins are extremely versatile products that are widely used in construction for coatings, adhesives, primers, and sealers. Occupational exposures to epoxies cause allergic contact dermatitis, occupational asthma, hypersensitivity pneumonitis (epoxy-resin lung) and acute decline in lung function. Despite these health concerns, there is a striking paucity of quantitative exposure data to epoxy resins in construction. The lack of practical analytical methods and suitable personal samplers for monitoring of reactive two-component epoxide systems in real-world applications has been an unmet challenge for decades. Sampling and analysis methods for epoxies should be able to collect the paint aerosols efficiently, stop polymerization reactions at the time of sample collection, and subsequently provide detailed multispecies characterization of epoxides, as well as the total epoxide group (TEG) content of a sample, to properly document the chemical composition of exposures to epoxide paints. In this work, we present the development and application of two new complementary quantitative analytical methods-liquid chromatography-tandem mass spectrometry with online ultraviolet detection and ion chromatography (IC)-for multispecies characterization of raw products, as well as inhalation and skin exposures to epoxy formulations in real-world construction applications. A novel personal sampler, CIP-10MI, was used for personal sampling of airborne epoxies. We report for the first time the results of personal inhalation and potential skin exposures to individual monomers and oligomers of bisphenol A diglycidyl ether (BADGE), as well as TEG, during metal structure coatings in construction; compare analytical results of the two analytical methods; and provide recommendations for method selection in future field studies. High inhalation and potential skin exposures to epoxies point to the need for interventions to reduce exposures among painters in construction.

Exposures and urinary biomonitoring of aliphatic isocyanates in construction metal structure coating

BACKGROUND

Isocyanates are highly reactive chemicals used widely in metal structure coating applications in construction. Isocyanates are potent respiratory and skin sensitizers and a leading cause of occupational asthma. At present, there is no cure for isocyanate asthma and no biomarkers of early disease. Exposure reduction is considered the most effective preventive strategy. To date, limited data are available on isocyanate exposures and work practices in construction trades using isocyanates, including metal structure coatings.

OBJECTIVES

The primary objectives of this work were: i) to characterize isocyanate inhalation and dermal exposures among painters during metal structure coating tasks in construction; and ii) to assess the adequacy of existing work practices and exposure controls via urinary biomonitoring pre- and post-shift.

METHODS

Exposures to aliphatic isocyanates based on 1,6-hexamethylene diisocyanate (1,6-HDI) and its higher oligomers (biuret, isocyanurate and uretdione) were measured among 30 workers performing painting of bridges and other metal structures in several construction sites in the Northeastern USA. Exposure assessment included simultaneous measurement of personal inhalation exposures (n = 20), dermal exposures (n = 22) and body burden via urinary biomonitoring pre- and post-shift (n = 53). Contextual information was collected about tasks, processes, materials, work practices, personal protective equipment (PPEs) and exposure controls, work histories, and environmental conditions.

RESULTS

Breathing zone concentrations were the highest for biuret (median, 18.4 μg/m³), followed by 1,6-HDI monomer (median, 3.5 μg/m³), isocyanurate (median, 3.4 μg/m³) and uretdione (median, 1.7 μg/m³). The highest exposures, measured during painting inside an enclosed bridge on a hot summer day, were: 10,288 μg/m³ uretdione; 8,240 μg/m³ biuret; and 947 μg/m³ 1,6-HDI. Twenty percent of samples were above the NIOSH ceiling exposure limit for 1,6- HDI (140 μg/m³) and 35% of samples were above the UK-HSE ceiling for total isocyanate group (70 μg NCO/m³). Isocyanate loading on the gloves was generally high, with a median of 129 μg biuret/pair and maximum of 60.8 mg biuret/pair. The most frequently used PPEs in the workplace were half-face organic vapor cartridge (OVC) respirators, disposable palmar dip-coated polymer gloves, and cotton coveralls. However, 32% of workers didn't wear any respirator, 47% wore standard clothing with short-sleeve shirts and 14% didn't wear any gloves while performing tasks involving isocyanates. Based on biomonitoring results, 58.4% of urine samples exceeded the biological monitoring guidance value (BMGV) of 1 μmol hexamethylene diamine (HDA)/mol creatinine. Post-shift geometric mean HDA normalized to specific gravity increased by 2.5-fold compared to pre-shift (GM, 4.7 vs. 1.9 ng/mL; p value, < 0.001), and only 1.4-fold when normalized to creatinine.

CONCLUSIONS

Exposure and biomonitoring results, coupled with field observations, support the overall conclusions that (i) substantial inhalation and dermal exposures to aliphatic isocyanates occur during industrial coating applications in construction trades; that (ii) the current work practices and exposure controls are not adequately protective. High urinary creatinine values in the majority of workers, coupled with significant cross-shift increases and filed observations, point to the need for further investigations on possible combined effects of heat stress, dehydration, and nutritional deficiencies on kidney toxicity. Implementation of comprehensive exposure control programs and increased awareness are warranted in order to reduce isocyanate exposures and associated health risks among this cohort of construction workers.

Testing of Disposable Protective Garments Against Isocyanate Permeation From Spray Polyurethane Foam Insulation

Background

Diisocyanates (isocyanates), including methylene diphenyl diisocyanate (MDI), are the primary reactive components of spray polyurethane foam (SPF) insulation. They are potent immune sensitizers and a leading cause of occupational asthma. Skin exposure to isocyanates may lead to both irritant and allergic contact dermatitis and possibly contribute to systemic sensitization. More than sufficient evidence exists to justify the use of protective garments to minimize skin contact with aerosolized and raw isocyanate containing materials during SPF applications. Studies evaluating the permeation of protective garments following exposure to SPF insulation do not currently exist.

Objectives

To conduct permeation testing under controlled conditions to assess the effectiveness of common protective gloves and coveralls during SPF applications using realistic SPF product formulations.

Methods

Five common disposable garment materials [disposable latex gloves (0.07 mm thickness), nitrile gloves (0.07 mm), vinyl gloves (0.07 mm), polypropylene coveralls (0.13 mm) and Tyvek coveralls (0.13 mm)] were selected for testing. These materials were cut into small pieces and assembled into a permeation test cell system and coated with a two-part slow-rise spray polyurethane foam insulation. Glass fiber filters (GFF) pretreated with 1-(9-anthracenylmethyl)piperazine) (MAP) were used underneath the garment to collect permeating isocyanates. GFF filters were collected at predetermined test intervals between 0.75 and 20.00 min and subsequently analyzed using liquid chromatography-tandem mass spectrometry. For each garment material, we assessed (i) the cumulative concentration of total isocyanate, including phenyl isocyanate and three MDI isomers, that effectively permeated the material over the test time; (ii) estimated breakthrough detection time, average permeation rate, and standardized breakthrough time; from which (iii) recommendations were developed for the use of similar protective garments following contamination by two-component spray polyurethane foam systems and the limitations of such protective garments were identified.

Results

Each type of protective garment material demonstrated an average permeation rate well below the ASTM method F-739 standardized breakthrough rate threshold of 100.0 ng/cm2 min-1. Disposable latex gloves displayed the greatest total isocyanate permeation rate (4.11 ng/cm2 min-1), followed by the vinyl and nitrile gloves, respectively. The Tyvek coverall demonstrated a greater average rate of isocyanate permeation than the polypropylene coveralls. Typical isocyanate loading was in the range of 900 to 15,000 ng MDI/cm2.

Conclusion

Permeation test data collected during this study indicated that each type of protective garment evaluated, provided a considerable level of protection (i.e. 10-110-fold reduction from the level of direct exposure) against the isocyanate component of the SPF insulation mixture. Nitrile gloves and polypropylene coveralls demonstrated the lowest rate of permeation and the lowest cumulative permeation of total isocyanate for each garment type.

Assessment and control of exposures to polymeric methylene diphenyl diisocyanate (pMDI) in spray polyurethane foam applicators

In this work we characterize personal inhalation and dermal exposures to diphenyl methane diisocyanate (MDI) and other species in polymeric MDI (pMDI) formulations during spray polyurethane foam (SPF) insulation at 14 sites in New England. We further assess the adequacy of current workplace practices and exposure controls via comparative urinary biomonitoring of the corresponding methylene diphenyl diamine (MDA) pre- and post-shift. MDI and pMDI are potent dermal and respiratory sensitizers and asthmagens, strong irritants of the skin, eyes, and the respiratory tract, and may cause skin burns. This study is the first comprehensive report to-date on the work practices, inhalation and dermal exposures to isocyanates and effectiveness of existing controls during SPF applications. Breathing zone exposures to 4,4' MDI (n = 31; 24 sprayers, 7 helpers) ranged from 0.9 to 123.0 μg/m3 and had a geometric mean (GM) of 13.8 μg/m3 and geometric standard deviation (GSD) of 4.8. Stationary near field area samples (n = 15) were higher than personal exposures: GM, 40.9 (GSD, 3.9) μg/m3, range 1.4-240.8 μg/m3. Sixteen percent of personal air samples and 35% of area samples exceeded the National Institute for Occupational Health and Safety's (NIOSH) full shift recommended exposure limit (REL) of 50 μg/m3, assuming zero exposure for the unsampled time. 4,4' MDI load on the glove dosimeters had a GM of 11.4 (GSD 2.9) μg/glove pair/min, suggesting high potential for dermal exposures. Urinary MDA had a GM of 0.7 (GSD, 3.0) μmol MDA/mol creatinine (range, nd-14.5 μmol MDA/mol creatinine). Twenty-five % of urine samples exceeded the Health and Safety Executive (HSE) biological monitoring guidance value (BMGV) of 1 μmol MDA/mol creatinine. We further report on field observations regarding current exposure controls, discuss implications of these findings and opportunities for improving work practices to prevent isocyanate exposures during SPF insulation.

Exposure to Diisocyanates and Their Corresponding Diamines in Seven Different Workplaces

Biological monitoring to assess exposure to diisocyanates in the workplace is becoming increasingly widespread due to its relative ease of use and ability to look at all exposure routes. Currently, biological monitoring measures the corresponding isocyanate-derived diamine in urine, after hydrolysis. Because of this, any exposure to the diamines themselves released during the industrial process could confound the assessment of diisocyanate exposure. This paper reports an initial assessment of the extent of diamine formation and exposure during different processes involving diisocyanates including casting, grouting, core making, spray painting, foam blowing, and floor screeding. Air monitoring and glove analysis were conducted for both the relevant diisocyanate (measured as total NCO) and its corresponding diamine; urine samples were analysed (after hydrolysis) for the isocyanate-derived diamine. Processes that generated aerosols (as demonstrated by impinger analysis) such as spray painting and foam blowing were associated with the detection of diamines. Those processes that did not generate aerosols (casting, grouting, core making, and screeding) had no diamines detected, either in air or on gloves. In spray-painting tasks, diamines were a minor component (<15%) of the ambient concentration whereas in the foam blowing processes, where water is added to the process, diamine generation is more marked (up to eight times the airborne NCO concentration). Some non-aerosol processes gave rise to substantial diamine levels in urine (in exceedance of international guidance values, >5 µmol mol-1 creatinine) despite airborne levels being well within occupational exposure limits (20 µg m-3 total NCO in Great Britain); measurement data and statistical modelling indicated that skin absorption was the most likely exposure route. Foam blowing exposures were more complex, but urinary levels were greater than those expected from diisocyanate inhalation alone (measured as total NCO). This study provides evidence that biological monitoring for diisocyanates based on measuring the corresponding diamine in urine is valid, although any co-exposure to diamines themselves should be considered when interpreting results. It also demonstrates the potential for substantial skin absorption of diisocyanates in certain processes such as floor screeding and foam production.

Residual Isocyanates in Medical Devices and Products: A Qualitative and Quantitative Assessment

We conducted a pilot qualitative and quantitative assessment of residual isocyanates and their potential initial exposures in neonates, as little is known about their contact effect. After a neonatal intensive care unit (NICU) stockroom inventory, polyurethane (PU) and PU foam (PUF) devices and products were qualitatively evaluated for residual isocyanates using Surface SWYPE™. Those containing isocyanates were quantitatively tested for methylene diphenyl diisocyanate (MDI) species, using UPLC-UV-MS/MS method. Ten of 37 products and devices tested, indicated both free and bound residual surface isocyanates; PU/PUF pieces contained aromatic isocyanates; one product contained aliphatic isocyanates. Overall, quantified mean MDI concentrations were low (4,4'-MDI = 0.52 to 140.1 pg/mg) and (2,4'-MDI = 0.01 to 4.48 pg/mg). The 4,4'-MDI species had the highest measured concentration (280 pg/mg). Commonly used medical devices/products contain low, but measurable concentrations of residual isocyanates. Quantifying other isocyanate species and neonatal skin exposure to isocyanates from these devices and products requires further investigation.